004
FXUS66 KMTR 070031
AFDMTR

Area Forecast Discussion
National Weather Service San Francisco CA
531 PM PDT Mon Oct 6 2025

...New AVIATION...

.KEY MESSAGES...
Updated at 222 PM PDT Mon Oct 6 2025

 - Warmer and drier conditions through Tuesday, with moderate
   offshore wind expected in the higher elevations

 - Cooler, unsettled weather returns late this week

&&

.SHORT TERM...
Issued at 222 PM PDT Mon Oct 6 2025
(This evening through Tuesday)

Offshore winds prevail in the higher elevations this afternoon, yet
that remain weak to moderate in strength. This has allowed for
temperatures to rapidly warm into the mid 70s to lower 80s across
much of the region. Slightly cooler conditions prevail along the
immediate coast where onshore winds have returned. Temperatures this
afternoon will peak in the low to mid 70s along the immediate
coastline with low to upper 80s across inland areas. Downtown San
Francisco has around a 14% probability of exceeding 85 degrees F
with southeast portions of the city at around 30%. Places such as
Novato, San Rafael, San Mateo, Redwood City, and Gilroy have a 30-
60% chance of exceeding 90 degrees F.

Temperature begin to cool just before sunset with overnight lows
dropping into the mid 50s to lower 60s across much of the region.
Low clouds and/or fog have the greatest potential for reaching the
San Mateo Peninsula and around the Monterey Bay region late tonight
and into early tomorrow morning. However, any low clouds/fog that do
develop will quickly retreat to the coast by mid morning.

Offshore winds will increase once again tonight, yet are expected to
be weaker than this morning. They will be strongest in the North Bay
and East Bay higher elevations. As such, Tuesday will be equally as
warm as today with the interior warming by a few degrees. However,
coastal locations have the potential to be a few degrees cooler than
today depending on when onshore flow returns.

&&

.LONG TERM...
Issued at 222 PM PDT Mon Oct 6 2025
(Tuesday night through next Sunday)

Onshore flow will return regionwide on Wednesday as an upper level
trough approaches the Pacific Northwest coast. This will result in a
significant cool down with temperatures returning to near or below
seasonal averages. Chances for rain return by early Friday morning
as a frontal boundary approaches the North Bay. The boundary is
forecast to shift southward through the day on Friday and into
Friday night bringing rain chances as far south as the Santa Cruz
Mountains. There remains a great deal of uncertainty on the on
potential for rain through the weekend as there is a lack of
consensus in the overall synoptic pattern. Be sure to stay up-to-
date with the latest forecast information as we get closer to the
weekend.

&&

.AVIATION...
(00Z TAFS)
Issued at 531 PM PDT Mon Oct 6 2025

It`s VFR except along the immediate coast around the Monterey Bay
to Big Sur satellite shows areas of fog and stratus /IFR-LIFR/.
The marine layer depth remains near or at sea level under thermal
ridging aloft. The WMC-SFO pressure gradient is 9.0 mb, the SFO-SAC
pressure gradient is flat and the ACV-SFO and SMX-SFO gradients are
2.5 mb to 1.8 mb respectively. At the surface there is currently
a mix of offshore winds (mainly away from the coastline and bays)
and onshore winds (closest to and along the coastline and bays).
Dry conditions support ongoing VFR except nocturnal cooling tonight
to daybreak Tuesday morning supports redevelopment of shallow marine
layer fog and stratus /IFR-LIFR/ with local intrusions of fog and
stratus occurring. Additionally a few patches of valley fog may
develop due to radiative cooling. A shallow marine layer is otherwise
still fairly easy to mix out quickly under an early October sun, as
expected Tuesday.

Vicinity of SFO...VFR. West to northwest wind near 10 knots decreasing
and becoming light northeast tonight and Tuesday morning. Wind west
to northwest near 10 knots Tuesday afternoon and early evening.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...It`s VFR except satellite shows areas of
fog and stratus /IFR-LIFR/ around the Monterey Bay. The current
surface winds and transport of fog and stratus is somewhat reflective
of a southerly wind reversal e.g. the recent SMX-SFO pressure gradient
is 1.8 mb. The 18z NAM has a better handle on the SMX-SFO gradient
than does recent HRRR output, both forecast the SMX-SFO gradient
continuing/developing tonight and Tuesday; good to keep in mind
with respect to potential fog and stratus advection.

Radiative cooling tonight to daybreak Tuesday resulting in patchy
valley fog may merge with coastal fog and stratus /IFR-LIFR/ steered
by surface to near surface winds. With respect to forecast winds,
expect onshore winds 10 to 15 knots this evening becoming light
and variable to light southeast tonight and Tuesday morning.
Onshore winds 10 knots redeveloping Tuesday afternoon.

&&

.MARINE...
(Today through Saturday)
Issued at 222 PM PDT Mon Oct 6 2025

Light to moderate winds accompanied by low to moderate seas will
prevail through Tuesday. An approaching system will begin to
increase winds and seas mid to late week.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...None.
&&

$$

SHORT TERM...RGass
LONG TERM....RGass
AVIATION...Canepa
MARINE...BFG

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